The present invention relates generally to data collection devices adapted for reading bar codes and other dataforms, and more particularly to a method and apparatus for minimizing power consumption in such devices.
Portable data collection devices are widely used in the manufacturing, service and package delivery industries to perform a variety of on-site data collection activities. Such portable data collection devices often include integrated bar code dataform readers adapted to read bar code dataforms affixed to products, product packaging and/or containers in warehouses, retail stores, shipping terminals, etc. for inventory control, tracking, production control and expediting, quality assurance and other purposes.
Bar code dataforms come in a variety of different formats including one and two dimensional bar codes, matrix codes and graphic codes, as well as words and numbers and other symbols, which may be printed or etched on paper, plastic cards and metallic and other items. For example, a one dimensional bar code dataform typically consists of a series of parallel light and dark rectangular areas of varying widths. The light areas are often referred to as xe2x80x9cspacesxe2x80x9d and the dark areas as xe2x80x9cbarsxe2x80x9d. Different widths of bars and spaces define different characters in a particular bar code dataform.
Data originally encoded in a dataform is recovered for further use in a variety of ways. For example, a printed bar code may be illuminated to derive reflectance values which are digitized, stored in buffer memory and subsequently decoded to recover the data encoded in the bar code. The printed bar code may be illuminated using a laser, an array of LEDs, ambient light, or the like. The light reflected from the printed bar code typically is captured using a photosensor such as, for example, a CCD detector, CMOS detector, etc.
A problem associated with conventional dataform readers is power consumption. The reader devices are typically used for short periods of time, between which the units are inactive. Conventional handheld dataform readers typically include two major components housed within a plastic enclosure. A scan engine is provided for reading a dataform and encoding the data therefrom, and a host interface board is included for providing power to the scan engine and for communicating data from the scan engine to other devices, such as computers, modems, and/or transmitters. The scan engine and the interface are commonly separate circuit boards or modules, interfacing via one or more cables and/or connectors.
Many mobile or portable data collection devices are powered via batteries. In such battery powered devices, it is desirable to minimize the frequency of battery replacements or recharges. As such, minimizing power consumption is an important design consideration. Some conventional scan engine units include circuitry to implement a low power or sleep mode, which may be engaged based upon inactivity for a certain time period. However, in present designs, only the scan engine unit enters into a sleep mode, while the interface board circuitry power consumption continues. Accordingly, there remains a strong need for further reducing the power consumption of handheld data collection devices, with minimal cost increase and/or modification to the components thereof.
The present invention includes a method and apparatus providing reduced data collection device power consumption, which utilizes existing scanning engine components. The invention may be applied in many systems which include a master component obtaining power via a slave component. However, the invention finds particular utility in data collection devices having a scan engine component and an interface component, such as portable hand-held bar code dataform readers.
According to one aspect of the invention, there is provided a method for reducing power consumption in a data collection device. The method includes providing a power detector in the interface component, sensing power delivered to the scan engine component using the power detector, and selectively reducing power delivered to at least a portion of the interface component according to the sensed power delivered to the scan engine component. The portion of the interface component for which power is selectively reduced may include a communications transceiver. For example, where a data collection device, such as a portable bar code reader includes a scan engine component deriving power from a power source via a host interface circuit board with a communications transceiver, the invention allows a power detector to selectively place the communications transceiver (and/or any other component of the interface board) in a low power state based on the power drawn by the scan engine component.
The scan engine may be adapted to enter a low power state, for example, where no user activity has occurred for a predetermined time period. The power detector according to an aspect of the invention may sense the reduced power consumption of the scan engine component via a current sensor, and selectively power down one or more components one the interface board. The provision of a power detector component on the interface board employs the low power mode logic mechanism of the scan engine component through sensing the power passing through the interface board from the power source to the scan engine. The invention thus provides a low cost solution to the problem of communications transceivers and other interface board components drawing power when the scan engine for which they provide service is in a low power or xe2x80x98sleepxe2x80x99 mode. In addition, no modifications to the scan engine are required, since the invention utilizes existing power feed signals on the interface board itself. It will be appreciated that although the power detector component may be a separate module or circuit board within a data collection device, that the power detector may be incorporated directly into the host interface board of such devices in accordance with another aspect of the invention.
According to another aspect of the invention, the power detector comprises a current detector adapted to sense current delivered to the scan engine component. In this regard, sensing the power delivered to the scan engine component in the methodology of the invention may further comprise determining whether the current delivered to the scan engine component is less than a threshold value. The threshold may represent, for example, a current level lower than the normal operating current of the scan engine component and higher than the low power or xe2x80x98sleepxe2x80x99 mode current draw of the scan engine. Accordingly, selectively reducing power delivered to a portion of the interface component according to the sensed power delivered to the scan engine component may further comprise selectively reducing the power delivered to a portion of the interface component if the current delivered to the scan engine component is less than the threshold value.
In this fashion, the power detector may determine that the scan engine is in xe2x80x98sleepxe2x80x99 mode, and selectively power down one or more interface board components accordingly. Although the invention is illustrated herein in association with powering down a communications transceiver upon detection that a collection device scan engine has entered xe2x80x98sleepxe2x80x99 mode, it will be appreciated that any or all the circuitry on an interface board in such a device may be likewise powered down, and that the invention may be employed in devices other than bar code readers and data collection devices. In addition, it will be appreciated by those skilled in the art that forms of power draw sensors other than current sensing devices may be employed, which are contemplated as within the scope of the invention.
In accordance with another aspect of the invention, there is provided a data collection device comprising a scan engine component, an interface component, a power source component adapted to deliver power to the scan engine component and the interface component, means for sensing power delivered to the scan engine component, and means for selectively reducing power delivered to at least a portion of the interface component according to the sensed power delivered to the scan engine component. The portion of the interface component for which power is selectively reduced may include a communications transceiver, and the means for sensing power delivered to the scan engine component may comprise a current detector which is adapted to sense current delivered to the scan engine component and to determine whether the current delivered to the scan engine component is less than a threshold value. In addition, the means for selectively reducing power delivered to a portion of the interface component may include a switching device adapted to selectively reduce the power delivered to a portion of the interface component if the current delivered to the scan engine component is less than the threshold value.
According to yet another aspect of the invention, a data collection apparatus is provided, which includes a scan engine component adapted to read a dataform (e.g., a bar code), a power source adapted to provide power to the scan engine, and an interface component receiving power from the power source and having a communications transceiver and a power detector component adapted to sense power delivered from the power source to the scan engine component and to selectively reduce power delivered from the power source to the communications transceiver according to the sensed power delivered to the scan engine component. The power detector component may further include a current sensor, a comparator, and a switch, wherein the current sensor is adapted to sense the current delivered to the scan engine component and to provide an output signal representative of the current delivered to the scan engine. In this regard, the comparator may be adapted to receive the output signal from the current sensor and to compare the value of the output signal to a threshold, and the switch may be adapted to selectively reduce power delivered from the power source to the communications transceiver according to an output signal from the comparator.
According to still another aspect of the invention, there is provided a method of reducing power consumption in a system having a master component, a slave component, a power source providing power to the master component and the slave component, and a power detector component adapted to sense power provided to the master component and to control the power provided to the slave component. The method includes sensing power provided to the master component using the power detector component, and controlling the power provided to the slave component using the power detector component according to the power provided to the master component. The method may further include comparing the power provided to the master component with a threshold, wherein controlling the power provided to the slave component comprises selectively reducing the power provided to the slave component if the power provided to the master component is less than the threshold.
The power detector component may advantageously include a current sensor adapted to sense the current delivered to the master component, a comparator component receiving a first input signal from the current sensor representative of the current delivered to the master component and having a second input signal representative of the threshold, and a switch movable between an open state and a closed state controlling the power provided to the slave component according to a control signal received from an output of the comparator. In this regard, selectively reducing the power provided to the slave component may comprise moving the switch to the open state via the control signal form the output of the comparator if the first input signal representative of the current delivered to the master component is less than the second input signal representative of the threshold. In addition, where the master component (e.g., a data collection device scan engine) has a normal operating mode corresponding to a first current value and a low power mode corresponding to a second current value, the first current value being greater than the second current value, and wherein the threshold has a value between the first and second current values, the power thus provided to the slave component may be selectively reduced when the master component is in the low power mode, in order to achieve power consumption savings when the unit is not being operated. In this regard, the master component may be a data collection device scan engine, and the slave component may be a data collection device communications transceiver.
In accordance with yet another aspect of the invention, there is provided a data collection device, comprising a master component, a slave component, a power source adapted to provide power to the master component and the slave component, and a power detector component adapted to sense power provided to the master component and to selectively control the power provided to the slave component according to the sensed power provided to the master component. The master component may include a scan engine, and the slave component may comprise a communications transceiver.